In recent years, an organic EL (Electro Luminescence) display apparatus has attracted because of its small thickness, light weight, and high response speed. The organic EL display apparatus includes a plurality of pixel circuits arranged in a two-dimensional form. The pixel circuits of the organic EL display apparatus each include an organic EL element and a driving transistor connected in series to the organic EL element. The driving transistor controls the amount of a current flowing through the organic EL element, and the organic EL element emits light with luminance depending on the flowing current.
Variations in characteristics of elements in pixel circuits occur during a production process. Furthermore, the characteristics of elements in the pixel circuits change with passage of time. For example, characteristics of driving transistors degrade individually depending on light emission luminance or light emission time. As with the driving transistors, characteristics of organic EL elements also degrade. Therefore, even when there is no difference in voltage applied to gate terminals of driving transistors, a variation occurs in light emission luminance among organic EL elements.
In view of the above, to achieve high image quality in displaying in organic EL display apparatuses, it is known, as a method, to correct an image signal so as to compensate for variations in characteristics among organic EL elements or driving transistors or as to compensate for changes in characteristic with time. For example, PTL 1 discloses an organic EL display apparatus configured such that voltages between terminals of organic EL elements, which occur when a calibration current is passed through each organic EL element, are measured, and an image signal is corrected based on the measured voltages thereby compensating for characteristic changes of the organic EL elements.